Aerobic exercise has become a way of life in America, and is fast becoming a major interest of Japanese and European society. Exercise equipment has become more effective and often more desirable in competition with running, aerobic dancing, etc. There are approximately 10,000 health clubs in the United States, and a recent trade association survey of members indicates that aerobic equipment topped the list of amenities to be added to health club equipment.
To win the competition with running and aerobic dancing, aerobic exercise equipment has had to become much more sophisticated, and as a result has become more costly. When used in health clubs and other multi-user institutions, exercise equipment requires exceptional ruggedness and resistance to abuse. As a result, exercise equipment intended for institutional use has grown in cost because of both sophistication and ruggedness requirements.
The cost of manufacturing aerobic exercise equipment in general can be conveniently grouped in the following categories of components: energy absorption, e.g. shunted motor generators to stress the user; structure, e.g. frames, to support the user and resist the forces that use produces; instrumentation to report and control exercise activity; and aesthetics, e.g. covers.
Aside from cost, one of the main problems with exercise equipment is that it is not used because exercise is not inherently fun. Exercise equipment thus has to have something added to become fun. Like many activities which require motivation, exercise often does better when there is a social or group involvement. The success of aerobic dancing is greatly related to the interaction factor. Health clubs have sought to supply this motivation with competitions such as tennis tournaments and tennis ladders. To bring interaction to machine exercise use, clubs offer ladder-like posted rankings based on numerical accomplishment. They generate interaction, but not as much as the head-to-head competition on a common field of play. It will be noted that people join health clubs to be involved with other people. Other people make exercise more like fun. Often interaction with other people, not exercise, is the primary reason people join health clubs. The more intimate the involvement, the better either the fun or social objectives are met. In the past, the norm is to prevent interactive involvement by providing single-user machines, or ganged machines in which the users either face in the same direction or face away from each other. Thus no social or competitive interactive activity is possible for these machines.
Thus, exercise equipment has existed that accommodates multiple users on a common machine. However, none of the machines have diammetrically-opposed, dual facing independently operable exercise stations which would promote both social and face-to-face interactivity. Moreover, no equipment exists which provides face-to-face competition in sports where none exists normally; such as running, bicycling or rowing where the participants do not normally face each other. Thus, in prior exercise equipment, the users were limited to facing in one direction or away from each other in independent exercise. Machines dedicated to joint activity such as the common seesaw are not flexible enough for the institutional requirements of a user being able to choose either an independent or interactive mode of use. However, one prior art multi-user machine, the Versa Climber, does provide independent stations on a base which more or less face each other. Here, however, there is no suggestion of interactive components and in fact completely independent controls are provided for each exercise station. Also there is no unobstructed view of even the head of a person at another station which prevents interactive exercise.
Note also that in universal apparatus, the individuals are not forced to face each other. Thus, none of the current equipment provides face-to-face use on a common machine, and all aerobic exercise machines require the purchase of a virtually complete second machine if two users are to be accommodated simultaneously.
As to safety, it will be appreciated that aside from the desirability of providing face-to-face interaction between the participants, when providing for single user devices one of the basic problems is the stability of the device. The overturn moment is of course important when various lever arms are extended beyond a point of pivot, such as is common with respect to reciprocating arm exercise stair type devices. Moreover, the weight of the device base must usually be increased so as to prevent vibration and overturning in both longitude and lateral directions. Thus for single exercise devices the mass of the device is oftentimes increased to provide stability, while at the same time not accommodating more than one user. It will be appreciated that the force applied to any exercise device is the mass of the user times gravity plus run acceleration. To this is often added a pull up force when an individual grabs a hand rail which adds to weight and acceleration. Thus, the forces applied can be significant. For instance, stairclimbers used by obesity clinics to fill exercise prescriptions for clients weighing up to and in excess of 400 pounds speak to the increase of user mass which must be accommodated by the exercise machine. Moreover, professional or college football teams use stairclimbing type devices for linemen that weigh up to 330 pounds. This presents a problem for the single user exercise machine in that the structural parts of the machine must withstand both the weight of a heavy individual and the torques he can generate. Note that such athletes can lift over 300 pounds and can accelerate to a 3.5 minute mile in less than a second. It will therefore be appreciated that single user machines must accommodate to such large applied forces.
Another consideration is the length of a lever arm for lever arm actuated exercise equipment. Such lever arm actuated exercise equipment includes a reciprocating arm exercise stair in which the length of the arm is a function of the step height required, and the maximum amount of angular deflection acceptable. The average step is 7 inches in height and a 12 inch or more step is necessary for a full range of motion on a stairclimber. The user's ankles must flex through approximately the same angular rotation as the arm. Experiments indicate that a user finds the angle of rotation becomes uncomfortable when the total arc movement is more than 24.degree.. As a result a minimum length arm must be 30 inches long. Such a machine must thus anticipate 1500 ft. lbs. of torque. When designing the counter-torque machine components, the length of the countering moment arm greatly affects the strength required of the components. As a practical matter of accommodating the user, the counter moment can not begin any closer than 20 inches from the point of application of user force. Therefore if the counter moment arm were just 10 inches beyond the 20 inch contact point on the 30 inch arm, the anti-torque components would be subjected to 1800 lbs. of stress. This is generally so large, that the design requires an extension of the counter moment components, eg. base. By way of example, an extension of the base by 10 inches, reduces the component stress to a more handable 900 lbs. Thus, if two stations are not combined, there can be no advantage taken in terms of half the moment supplied by the other station.
Another problem with single station machines is the problem of tip toward the user. Thus, designers of rotating arm exercise machines must consider counter-torque in relation to the safety concerns of avoiding the possibility of the machine tipping toward the user. While the possibility of users pulling climbers over on top of themselves is remote, even a small lifting of the machine during exercise can cause unbalance and lead to injury.
There are two important tip torques. The first is the torque applied by a user during exercise. The second tip torque occurs when the user leans back away from the machine while holding onto the machine. In each circumstance torque is a function of the distance between the force vector and the point at which the forward portion of the machine comes in contact with the floor. The exercise torques are generally so large in relation to the weight of the single user machine, they require the forward machine/floor contact point for the base to be extended out behind the user so there can be no exercise-induced tip torque. By way of example a four hundred pound user can get his center of gravity 6 inches out behind the forward machine/floor contact point. This will generate 200 ft. lb. of torque. A 100 lb. machine would thus have to have its center of gravity 24 inches away from the forward floor contact point, or a 200 lb. machine would have to have its center of gravity 12 inches from the floor contact point, to counter this tip forward torque. Thus single user machines require cumbersome space-consuming extensions to avoid tipping.
In summary, if the machine design puts the machine/floor contact point some significant distance behind the point at which the user applies force, or to which he can move his center of gravity, all tip concerns are eliminated, but at high cost due to extension of the base of the machine. As will be seen in a dual, diammetrically-opposed exercise station configuration, since an opposing station machine has its center of gravity a significant distance away from the machine/floor contact point of the other machine, the floor contact point for neither station has to be behind the user, and can be some significant distance in towards the center of the combined machine, thereby minimizing machine size and space.